Examples of Dye Sublimation Prints
Format (prints often 4 x 6 inches)
Diffuse continuous tone
Backprint
Linear pattern
Common Use Dates: 1995-Present
Alternate Names: D2T2, Dye Diffusion Thermal Transfer, Dye Sub, Thermal Dye Diffusion Transfer, Thermal Dye Sublimation, Thermal Dye Transfer (TDT)
Mistaken For: Chromogenic, digitally exposed chromogenic, photothermographic transfer (Pictrography)
Process Family(s): Digital, Thermographic, Dye, Paper support, Print
Dye sublimation – more accurately known as Dye Diffusion Thermal Transfer (D2T2) – is a digital printing process utilizing heat to form a dye image in a substrate. Despite its name, it is unlikely sublimation (the transition of a substance from the solid to gaseous phase without the intermediate liquid phase) occurs during printing. The process is best described as diffusion, however “dye sublimation” remains the preferred colloquial term.
The sublimation misnomer is rooted in the process’ history, commonly attributed to the textile industry. In 1957 Noël De Plasse, an employee of the textile company Lainière de Roubaix, discovered that certain dyes sublimate at high temperatures and reform as solids upon cooling. Although sublimation does not occur, the concept of heating dyes in order to diffuse them into a substrate was applied to digital imaging in 1982 when Sony engineer, Nobutoshi Kihara, used it to print video stills taken with a Mavica video camera. The first dye sublimation printer, The Sony Mavigraph, was commercially available by 1986.
Unlike other thermographic printing processes developed throughout the mid-twentieth century, D2T2 was able to produce prints closely resembling true photographs. Advances in the process proliferated and its popularity increased during the 1980s and 1990s as companies including Hitachi, Sharp, Kodak and Canon entered the market. Distinguishing the printing mechanism to be one of diffusion rather than sublimation (circa 1991) permitted a wider range of suitable image-forming dyes – early dyes were limited to a small selection of subliminal textile dyes. Furthermore, the fragility of early prints was mitigated by the introduction of protective overcoating in 1994. Prints made prior to this advancement were extremely susceptible to damage by light, pollution, humidity, heat, and water. Such improvements bolstered the popularity of dye sublimation printing. By the 2000s, desktop D2T2 printers and commercial print kiosks were in common use.
D2T2 printing systems rely on three main components: a thermal printhead, dye donor ribbon, and dye receiving substrate. Image formation occurs when dyes are transferred to the substrate from the ribbon by heat applied by the printer. First, a microprocessor breaks a digital image into cyan, magenta, and yellow (subtractive primary color) components. This information is used to control the output of the printer’s thermal array, a device containing a linear arrangement of tiny resistors. Resistors are individually heated to varying temperatures to control the amount of dye diffused, thereby permitting a wide tonal range in the final print.
The image is printed line by line as rows of dots. The intensity of color at each point is determined by the length and intensity of its resistor’s heat pulse. Thermal arrays contain between 200 and 600 heating elements per inch; more elements yield a finer print resolution. The donor ribbon, carrying the image dyes to be transferred, runs between the thermal array and the substrate. Ribbons are composed of a thin polyester film between a cross-linked and lubricated polymeric slip coat (facing the thermal head during printing) and a barrier layer made up of heat-resistant resins. Dyes rest on top of the barrier layer, which ensures they bond to the polyester film until heated. For full color printing, dyes are arranged in panels of yellow, magenta and cyan and three printing passes occur to overlay the three colors. In the printer, a platen roller presses the substrate against the thermal array. The ribbon runs between the substrate and the array with its dye coating facing the substrate’s receiving layer. As heat is applied, dyes diffuse from the ribbon into the substrate where they become fixed upon cooling. After a color layer prints, the substrate backs up and the next color is printed overtop. A panel holding a protective wax topcoating is printed last. This coating is applied by means of direct thermal transfer (D1T2) and covers the entire image.
Though D2T2 may be used to print on a wide variety of substrates, such as papers, plastics and textiles, RC paper substrates are most common in the realm of consumer printing. These are composed of multiple layers including a paper core coated with a dye receiving soluble polymer on one side and laminated paper or polyethylene film on the other. The front and back layers contain anti-slip silicone-based materials to prevent the ribbon from sticking during printing and to ensure smooth passage through the printer.
To the naked eye, D2T2 prints resemble true photographs. Under magnification they remain continuous in tone, but artifacts of processing, such as a faint grid pattern caused by the thermal array, are visible. Though a versatile printing method, D2T2 costs more and is less energy efficient than inkjet printing. Coated prints are highly resistant to water damage, humidity, and environmental pollution. However they possess moderate to high light sensitivity and are susceptible to fading if not housed in dark storage. Due to the nature of the process, they may also be damaged by heat, the application of which causes dyes to migrate within the receiving layer.